USB UART output buffer remains full after serial disconnect

[douglas.malnati]

Windows 11, NCS v2.3.0, VSCode

Hi, I am using the uart_poll_out API for communicating via USB serial.

For each character I want to output, I do this:

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uint32_t dtr;

uart_line_ctrl_get(DEV_UART_USB, UART_LINE_CTRL_DTR, &dtr);

if (dtr)

{

uart_poll_out(DEV_UART_USB, c);

}

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

uint32_t dtr;
uart_line_ctrl_get(DEV_UART_USB, UART_LINE_CTRL_DTR, &dtr);
if (dtr)
{
    uart_poll_out(DEV_UART_USB, c);
}

The other side of the serial connection can disconnect at any time.

I don't want my code to hang trying to write, that's why I checked the DTS beforehand, and basically throw away any data that won't get sent immediately.

The problem I have is:

- I am writing continuously

- The other side disconnects

- I attempt to detect that, and do, eventually, but not before the uart_poll_out puts a few characters into what I assume is an output buffer which fills up a short time later

Then, when the other side re-connects, the bytes that are sitting in the output buffer get sent.  This corrupts the datastream to the receiver as those bytes were for a different connection.

Is there a way to deal with this?

I would basically like to detect that I can't send data, and clear any existing output buffer at that time.

Or any other way to deal with this situation?

I'm not a serial expert and I only had the line_ctrl code because I saw it in an example.  Please let me know.

Thanks.